1. This invention relates to unstable ring-resonator lasers and especially to off-axis, unstable, ring-resonator lasers with a 90.degree. feedback-beam rotator.
2. High-energy lasers exhibit beam non-unifority due to gain-medium non-uniformities. Off-axis unstable resonators are subject to instabilities and wasted power because the self-reproducing ray travels at the edge of the gain medium.